Many polymeric materials have been evaluated for potential utility as contact lens material, but a very limited number of materials have been found to form contact lenses which are satisfactory. Advances in contact lens materials and techniques have come in small steps, which have been excruciatingly slow and difficult. Polymers and methods which appeared attractive have fallen by the wayside. The problems are myriad, and predictability is low. It is difficult and frequently impossible to predict optical quality, strength and flexibility, resistance to protein buildup, machining and fabrication characteristics, dimensional stability, oxygen permeability, and general biological compatibility. It is impossible to predict, or even to speculate as to possible optical, oxygen permeability, and biological characteristics of structural and industrial silanes such as disclosed by Campbell, U.S. Pat. No. 2,958,681 for example.
Reference is made to the literature, in texts, treatises and technical literature which describe silicon compounds, commonly referred to as silanes, particularly alkylsilanes. While the present invention departs from this chemistry in important and substantial ways, this body of chemistry is fundamental to the present invention.
Silane chemistry is quite well known and reported in the literature. An excellent treatment of the chemistry of silanes is given by Sommers, L. H.; Mitch, F. A.; and Goldberg, G. M., "Synthesis and properties of Compounds with a Framework of Alternatesilicon and Carbon Atoms," J.A.C.S., 71, 2746, (1949). Surveys of this body of chemistry are found in KIRK-OTHMER, ENCYCLOPEDIA OF CHEMICAL TECHNOLOGY, 3rd Ed. at Vol. 20, pp. 887-991. The chemistry of organosilicon compounds is described in ORGANOSILICON COMPOUNDS, Bazant, Chvalovsky and Rathovsky, Academic Press, Inc., New York, 1965.
Silanes have been utilized in preparative organic chemistry and for a number of specialty applications, including waterproofing compounds for mortar and fabrics and the like, as accelerators in some polymer operations, and as intermediates in the preparation of organosiloxanes.
Upchurch, U.S. Pat. Nos. 4,528,301 and 4,616,045 mention, inter alia, contact lenses of copolymers in which one monomer is selected from "a substituted polysiloxane such as dimethyl polysiloxane or a substituted silane" and refers to dimethyl, ethyl, phenyl, methoxy, vinyl, fluoropropyl, cyano, dimethylphenyl substituted silanes and mixtures of the same; however, this reference to silane monomers as constituents in contact lens polymers is apparently a shot in the dark. No examples of silane-containing contact lenses are given and it is not apparent from Upchurch, supra, that it would even be possible to prepare a silane-containing contact lens.
Takahashi, et al, U.S. Pat. No. 4,594,401 discloses contact lenses in which a substantial or major monomeric component in the polymer of which the lens is formed is trimethylsilylstyrene ##STR1## While Takahashi et al disclose an increase in oxygen permeability in lenses in which trimethylsilylstyrene is a major constituent, and suggest that a limited class of trimethylsilyl compounds, e.g. trimethylsilylmethyl methacrylate, trimethylsilylmethyl acrylate, trimethylsilylpropyl methacrylate, and trimethylsilylpropyl acrylate may be substituted, there is no disclosure or suggestion of the use of more complex disylylemethylenes as lens polymer constituents. In view of the high level of uncertainty and lack of predictability vis-a-vis whether or not a given polymer can be made to form lenses, whether it will be transparent, have a suitable refractive index or hardness, etc., one cannot predict from the prior art whether or not silylmethylene methacrylate compounds may be incorporated into polymers which will form suitable contact lenses.